Low temperature liquefied gas storage tank and tanker

ABSTRACT

A storage container constructed either as a tank or a tanker for storage of low-temperature liquids such as liquefied gases. The container is constructed as an outer vessel with a thermal insulation lining and an inner membrane structure consisting of two thin metallic membrane tanks one interiorly of the other. The innermost tank or vessel is thinner than the other inner tank and maintains the fluid-tightness of the container. A vacuum pump applies a vacuum to the space between the two inner tanks to detect leaks and maintains the innermost vessel from collapsing in a non-loaded condition.

United States Patent 1m Yamamoto 14 1 Apr. 3, 1973 54 LOW TEMPERATURE LHQUEEEED GAS 3,595,424 7 1971 Jackson ..114/74 A STORAGE TANK AND TANKER 962,710 6/1910 Levin ..220/9 C 1,088,194 2/1914 Whitton ..220/9 C [75] Inventor: Katsuro Ynmamoto, Tokyo, Japan [73] Assignee: Bridestone Liquefied Gas Company 'f Emmi'fe" joseph Leclail' Limited, Tokyo Japan Assistant Examiner-Allan N. Shoap Attorney-Robert E. Burns et a1. [22] Filed: Oct. 28, 1971 21 Appl. No.: 193,344 [571 ABSTRACT A storage container constructed either as a tank or a tanker for storage of low-temperature liquids such as [30] Foreign Apphcaflon Pnomy Dam liquefied gases. The container is constructed as an Oct. 31, 1970 Japan ..45/95630 outer vessel with a thermal insulation lining and an inner membrane structure consisting of two thin [52] U.S. Cl ..220/9 LG metallic membrane tanks one interiofly 0f the Other- [51] int. Cl. ..B65d 25/18 The innermost tank Vessel is thinner than the other [53 Fi l f Seal-c 220 9 g C; 114/74 A inner tank and maintains the fluid-tightness of the 1 container. A vacuum pump applies a vacuum to the [56] References Cited space between the two inner tanks to detect leaks and maintains the innermost vessel from collapsing in :1 UNITED STATES PATENTS non-loaded condition.

3,272,373 9/1966 Alleaume et a1. ..220/9 LG 9 Claims, 1 Drawing Figure 8 n u 6 1 ,111 M 3,

LOW TENIPERATURE LIQUEFIED GAS STORAGE TANK AND TANKER BACKGROUND OF THE INVENTION The present invention relates to a membrane-type storage container for use in storing a low-temperature liquefied gas that is gaseous at ordinary temperatures.

DESCRIPTION OF THE PRIOR ART Conventional membrane-type storage tanks comprise an outer shell made as a pressure resistant structure with a heat-insulating layer provided on the inside thereof. A membrane-type inner tank made of thin plate' and having a structure that can easily flex under the influence of internal pressure and temperature variations is in close contact with the surface of the heat-insulating layer and is disposed interiorly of the layer. The internal pressure in the membrane-type inner tank is transmitted through the heat-insulating layer to the outer shell. In the known membrane-type tank or containers it has also been necessary to provide a secondary barrier for temporarily stopping the liquefied gas in case it should leak out from the inner tank.

Since the secondary barrier needs to have not only resistance against the load and the low temperature of the liquid contained therein but also liquid-tightness, it is made of a costly material and is generally a complicated structure, thereby increasing the manufacturing costs of the entire container.

SUMMARY OF THE INVENTION An object of the present invention is to simplify the A structure of low-temperature liquid containers and to provide a safe membrane-type storage device for lowtemperature liquefied gases by eliminating the use of a secondary barrier of the type used in conventional lowtemperature storage tanks and providing the function of the secondary barrier in an inner tank. Additionally there is provided a second inner or innermost tank which displaces in accordance with the displacement of the inner tank in response to load and temperature variations of the liquid stored therein.

Another object of the invention is to provide a lowtemperature liquid storage container that is adapted to,

facilitate the supporting of the innermost or second inner tank and the detection of leakage of the liquid by reduction of the pressure in the space between the walls of said double-structured inner tank arrangement.

In order to achieve the above-mentioned objects, the storage container of the present invention has a second membrane structure or innermost tank provided inside of a first inner tank in close contact therewith and made of metallic thin plate having lesser thickness than the metallic thin plate used for the first inner tank. The inner tanks are disposed interiorly of an outer hull or shell made as a rigid structure provided with a compression-resistant heat-insulating layer on the inside thereof. The first inner tank of the membrane structure is disposed immediately adjacent the inside surfaces of the heat-insulating layer.

In the storage container according to the present invention, the outer shell, heat-insulating layer and first inner tank, in combination, support the load of a lowtemperature liquid or liquefied gas stored therein. At

the same time the first inner tank is adapted to protect the second inner tank which is provided on the inside thereof and made of thinner metallic plate as well as to perform the function of the usual secondary barrier. Therefore the thickness of the plate of the innermost tank can be reduced sufficiently since the function of the second inner tank is only to maintain fluidtightness, which, in turn, makes it possible to increase the adaptability of the storage container as a membrane structure. The invention achieves a very high reliability by use of the double-structured inner tank arrangement described above.

The storage container of the invention has the pressure in the space between the first and second inner tanks reduced by application of a vacuum thereto. By thus reducing the pressure the space between the walls of the double-structured inner tank arrangement, it becomes possible to easily detect any leak from the innermost or second inner tank by analyzing the gas taken from the space. By reducing this pressure it is also possible to support the upper part of the second inner tank so that it does not fall down or collapse because of its own weight even when the internal pressure in the second inner tank is at atmospheric pressure under a no-load condition since the second inner tank has the lesser thickness and must be drawn close to the interior surface of the relatively thicker first inner tank.

BRIEF DESCRIPTION OF THE DRAWING The appended drawing is a fragmentary cross section view of a hull or a tanker for carrying low temperature liquefied gas, as a preferred embodiment of the present invention.

Other objects and advantages will appear from the following description of an example of the invention, and the novel features will be particularly pointed out in the appended claims.

DESCRIPTION OF THE PREFERRED I EMBODIMENT In order that the invention may be fully understood, an embodiment thereof is described hereinafter as applied to a tanker for carrying low-temperature liquefied gas. Those skilled in the art will understand that the structure described herein with respect to a tanker can be used in the construction of storage containers ashore for storage of the low-temperature liquefied gas transported by tankers constructed according to the invention.

The accompanying drawing is a cross section view of a hull of a tanker, or it can be thought of as a stationary storage container, for carrying low-temperature liquefied gas, wherein an outer shell or hull 1 is provided with an inner bull or shell 1a lined interiorly with a heat-insulating layer 2. The heat-insulating layer 2 may be made of hard foamed polyurethane that can resist compression or it can be made of a powdery pearlite contained in a frame, for example a wooden frame, not shown, cooperating with the outer shell. The inner lining as a whole must be able to stand compression. Within the shell a membrane structure is provided comprising a first innertank 3 in contact with the compression-resistant heat-insulating layer 2, and inside of the first inner tank there is a second inner tank 30 constructed as a metallic membrane structure.

The first and second inner tanks 3 and 3a are both made of thin metallic plate, for example of low-temperature resistant materials such as nickel steel, stainless steel or aluminum. The innermost or second inner tank 3a is made of thinner plate than the first inner tank 3 on the outside thereof. The innermost tank 3a has a thickness of about 1 mm and the first inner tank 3 has a thickness of about 4 to 6 mm.

The first inner tank or vessel 3 is flexible and has a bottom, four side walls, four corners and areas of jointure joining the side walls and the edges of the bottom to the lower edges of the side walls. The areas of jointure each have an arcuate cross section and each define an arcuate edge of the inner vessel or tank 3 merging smoothly with respective ones of the lower four corners. The inner tank 3 has similar upper corners and areas of jointure joining the upper edges of the side walls with an open top.

The first inner tank 3 is in contact with the heat-insulating lining and its bottom spans the bottom inner lining in a loaded or non-loaded condition. The inner lining is configured to receive thereagainst respective lower and upper corners and the curved or arcuate areas of jointure at the top and bottom merging smoothly with the comers and the top and bottom edges of the side walls.

The second innermost tank or vessel has a bottom, side walls, comers and upper and lower arcuate areas of jointure joining the side walls and the edges of the bottom of an open top to the side walls. The corners and areas of jointure have an arcuate cross section in the manner of the first inner tank 3. The innermost vessel 3a is configured and dimensioned to fit snugly against the corresponding inner surfaces of the first inner vessel 3.

The openings at the tops of the two membrane vessels or tanks 3,3a are in registry as shown in the drawing. The marginal portions of the top openings bear against a flange of a rigid trunk extending through the inner and outer shells 1,1a and which is reinforced by brackets, for example at 5. Both marginal edge portions circumferentially of the openings of the two inner membrane tanks 3,341 are secured to the outer structure as shown and an airtight space exists between the two inner tanks.

The rigid-trunk 5 is also rigidly fitted, through supports 6,7 made of heat-insulating material, to the double shell 1 and by means of flanges at the upper and lower ends thereof. Heat-insulating material 8 is filled between the shell 1 and the trunk 5 so that the shell is not directly affected by the coldness in the inner tank. Provision for loading pipes, gas pipes and the like is made through the trunk 5. The opening in the trunk 5 is covered with an airtight cover, not shown, through which the pipes pass into the interior of the innermost vessel or tank 3a.

A vacuum pump is mounted between the outer and inner shells and has a suction pipe 10 connected to the airtight space between the first and second inner tanks 3,3a. The pressure in this airtight space is reduced to keep the first and second inner tanks 3 and 3a in substantially close contact with each other. Because of the application of the vacuum the first and second inner tanks 3 and 3a can integrally support themselves even when the internal pressure in the second inner tank 3a is reduced to atmospheric pressure when maintenance and inspection work are carried out thereon. The application of the vacuum has a particular advantage in providing an efficient support for the second inner tank 3a made of thin plate without causing any stress concentration thereon and to prevent the falling or collapse of the upper portion of the inner tank due to its own weight.

When low-temperature liquefied gas is filled in the second inner tank 3a, the first inner tank undergoes deformation under the influence of the load and the low temperature of the gas. However, since the second inner tank 3a is made of thinner plate than the first inner 3 and is kept close to the inside of the latter, it can freely change its form following the deformation of the first inner tank, thereby keeping itself free from undesirable stresses. In case a leak occurs in the second inner tank 30 it can be detected without delay by analyzing the gas sampled by the vacuum pump 9.

Since the first irmer tank 3 is made of thicker plate than the second inner tank 3a, the first inner tank 3 can provide liquid-tightness and sufficient strength as a secondary barrier, thereby increasing the reliability of the entire system. Also, this first inner tank 3 can be prepared with much ease, as compared with the conventional secondary barrier of complicated construction inserted between the heat-insulating walls. Moreover, it can sufliciently protect the second inner tank 3a by being in close contact with the outer surfaces thereof.

It will be understood that the membrane-type storage container for low-temperature liquefied gas according to the present invention provides a remarkably high reliability with a very simple structure. It enables the tankers for low-temperature liquefied gas and other similar carriers to be used under severe conditions and to safely accommodate and store a low-temperature liquefied gas.

What I claim and desire to secure by Letters Patent l. A storage container for storage of a low-temperature liquid such as a low-temperature liquefied gas comprising, a first inner vessel of flexible metallic material having a bottom, four side walls, four corners and areas of jointure joining the side walls and the edges of the bottom to the lower edges of the side walls, said areas of jointure each having an arcuate cross-section and each defining an arcuate edgeof said inner vessel merging smoothly with respective ones of said lower four corners, said first inner vessel having an open top, outer support means supporting the bottom and side walls of said first inner vessel in a loaded condition, said outer support means being defined by an outer vessel having an inner insulating lining having a surface spanned by the bottom of said inner vessel in a loaded and non-loaded condition and surfaces disposed to receive thereagainst respective lower corners of said first irmer vessel in a loaded condition and side surfaces against which the side walls bear when said container contains said liquefied gas, said insulation lining overly- I ing said open top of said inner vessel, means supporting said open top, a second innermost vessel of flexible metallic material of lesser thickness than said first inner vessel disposedinteriorly of said first inner vessel and having a bottom, side walls, corners and areas of jointure joining the side walls and the edges of the bottom to the lower edges of the side walls, said areas of jointure of said second innermost vessel having an arcuate cross section and each defining an arcuate edge of said second innermost vessel merging smoothly with respective ones of said lower four corners, said second innermost vessel having an open top in registry with the open top of said first inner vessel, said second innermost vessel being configured and dimensioned to fit snugly against the inner surfaces of the first inner vessel, and means maintaining a pressure differential between the vessels and the interior of the second innermost vessel and the exterior of the first inner vessel, effective to cause atmospheric pressure to maintain the second innermost vessel snugly against the first inner vessel when the second innermost vessel does not contain liquefied gas.

2. A storage container for storage of a low-temperature liquid such as a low-temperature liquefied gas according to claim 1, in which said means maintaining said pressure differential comprises vacuum-applying means to apply a vacuum between the interior of the first inner vessel and the exterior of the second inner vessel. 7

3. A storage container for storage of a low-temperature liquid such as a low-temperature liquefied gas according to claim 2, in which said vacuum-applying means comprises a vacuum pump.

4. A storage container for storage of a low-temperature liquid such as a low-temperature liquefied gas according to claim 2, in which said outer vessel comprises a trunk providing access to the interior of the two inner vessels.

5. A tanker for transporting low-temperature liquids such as low-temperature liquefied gases comprising, an outer hull, a rigid support interiorly of said hull having a compression-resistant, heat-insulating lining interiorly thereof, a flexible membrane structure interiorly of said heat-insulating lining and supported by said heatinsulating lining, said membrane structure comprising two flexible membrane-type tanks comprising a first inner tank made of thin, flexible metallic sheet, a second innermost tank interiorly of the first inner tank and having its outer surfaces in contact with the inner surfaces of the first inner tank, said-second innermost tank being made of flexible metallic sheet thinner than the sheet of said first inner tank, each of said two membrane-type tanks having a bottom, four side walls, four corners and areas of jointure joining the side walls and the edges of the bottom to the lower edges of the side walls, said areas of jointure each having an arcuate cross section and each defining an arcuate edge merging smoothly with respective ones of said lower four corners, each of said two membrane-type tanks having an open top and the openings therein being in registry, and means to reduce air pressure in a space between the two membrane-type tanks sufficiently to maintain the second innermost tank from collapsing from its own weight.

6. A tanker according to claim 5, in which said means to reduce air pressure in said space between the membrane-type tanks comprises means to detect leaks in the second innermost tank.

7. A tanker according to claim 5, in which said means to reduce air pressure in said space between the membrane-type comprises a vacuum pump having means to take a suction on said space.

8. A tanker for transporting low-temperature liquids such as low-temperature liquefied gases comprising, an outer hull, a rigid support interiorly of said hull and having a compression-resistant, heat-insulating lining interiorly thereof, a flexible membrane structure interiorly of said heat-insulating lining, said membrane structure comprising two flexible, membrane-type tanks comprising a first inner tank made of thin, flexible, metallic sheet, a second innermost tank interiorly of the first inner tank and having its outer surfaces in contact with the inner surfaces of the first inner tank, said second innermost tank being made of flexible metallic sheet thinner than the sheet of said first inner tank, each of said two membrane-type tanks having a bottom, four side walls, four corners and areas of jointure joining the side walls and the edges of the bottom to the lower edges of the side walls, said areas of jointure each having an arcuate cross section and each defining an arcuate edge merging smoothly with respective ones of said lower four corners, each of said two membranetype tanks having an open top and the openings therein being in registry, and means to apply a suction to a space between the two membrane-type tanks to detect the existence of a leak in said second innermost membrane-type tank.

9. A tanker according to claim 8, in which said means to apply a suction to said space comprises means to apply a vacuum to said space. 

1. A storage container for storage of a low-temperature liquid such as a low-temperature liquefied gas comprising, a first inner vessel of flexible metallic material having a bottom, four side walls, four corners and areas of jointure joining the side walls and the edges of the bottom to the lower edges of the side walls, said areas of jointure each having an arcuate cross-section and each defining an arcuate edge of said inner vessel merging smoothly with respective ones of said lower four corners, said first inner vessel having an open top, outer support means supporting the bottom and side walls of said first inner vessel in a loaded condition, said outer support means being defined by an outer vessel having an inner insulating lining having a surface spanned by the bottom of said inner vessel in a loaded and non-loaded condition and surfaces disposed to receive thereagainst respective lower corners of said first inner vessel in a loaded condition and side surfaces against which the side walls bear when said container contains said liquefied gas, said insulation lining overlying said open top of said inner vessel, means supporting said open top, a second innermost vessel of flexible metallic material of lesser thickness than said first inner vessel disposed interiorly of said first inner vessel and having a bottom, side walls, corners and areas of jointure joining the side walls and the edges of the bottom to the lower edges of the side walls, said areas of jointure of said second innermost vessel having an arcuate cross section and each defining an arcuate edge of said second innermost vessel merging smoothly with respective ones of said lower four corners, said second innermost vessel having an open top in registry with the open top of said first inner vessel, said second innermost vessel being configured and dimensioned to fit snugly against the inner surfaces of the first inner vessel, and means maintaining a pressure differential between the vessels and the interior of the second innermost vessel and the exterior of the first inner vessel, effective to cause atmospheric pressure to maintain the second innermost vessel snugly against the first inner vessel when the second innermost vessel does not contain liquefied gas.
 2. A storage container for storage of a low-temperature liquid such as a low-temperature liquefied gas according to claim 1, in which said means maintaining said pressure differential comprises vacuum-applying means to apply a vacuum between the interior of the first inner vessel and the exterior of the second inner vessel.
 3. A storage container for storage of a low-temperature liquid such as a low-temperature liquefied gas according to claim 2, in which said vacuum-applying means comprises a vacuum pump.
 4. A storage container for storage of a low-temperature liquid such as a low-temperature liquefied gas according to claim 2, in which said outer vessel comprises a trunk providing access to the interior of the two inner vessels.
 5. A tanker for transporting low-temperature liquids such as low-temperature liquefied gases comprising, an outer hull, a riGid support interiorly of said hull having a compression-resistant, heat-insulating lining interiorly thereof, a flexible membrane structure interiorly of said heat-insulating lining and supported by said heat-insulating lining, said membrane structure comprising two flexible membrane-type tanks comprising a first inner tank made of thin, flexible metallic sheet, a second innermost tank interiorly of the first inner tank and having its outer surfaces in contact with the inner surfaces of the first inner tank, said second innermost tank being made of flexible metallic sheet thinner than the sheet of said first inner tank, each of said two membrane-type tanks having a bottom, four side walls, four corners and areas of jointure joining the side walls and the edges of the bottom to the lower edges of the side walls, said areas of jointure each having an arcuate cross section and each defining an arcuate edge merging smoothly with respective ones of said lower four corners, each of said two membrane-type tanks having an open top and the openings therein being in registry, and means to reduce air pressure in a space between the two membrane-type tanks sufficiently to maintain the second innermost tank from collapsing from its own weight.
 6. A tanker according to claim 5, in which said means to reduce air pressure in said space between the membrane-type tanks comprises means to detect leaks in the second innermost tank.
 7. A tanker according to claim 5, in which said means to reduce air pressure in said space between the membrane-type tanks comprises a vacuum pump having means to take a suction on said space.
 8. A tanker for transporting low-temperature liquids such as low-temperature liquefied gases comprising, an outer hull, a rigid support interiorly of said hull and having a compression-resistant, heat-insulating lining interiorly thereof, a flexible membrane structure interiorly of said heat-insulating lining, said membrane structure comprising two flexible, membrane-type tanks comprising a first inner tank made of thin, flexible, metallic sheet, a second innermost tank interiorly of the first inner tank and having its outer surfaces in contact with the inner surfaces of the first inner tank, said second innermost tank being made of flexible metallic sheet thinner than the sheet of said first inner tank, each of said two membrane-type tanks having a bottom, four side walls, four corners and areas of jointure joining the side walls and the edges of the bottom to the lower edges of the side walls, said areas of jointure each having an arcuate cross section and each defining an arcuate edge merging smoothly with respective ones of said lower four corners, each of said two membrane-type tanks having an open top and the openings therein being in registry, and means to apply a suction to a space between the two membrane-type tanks to detect the existence of a leak in said second innermost membrane-type tank.
 9. A tanker according to claim 8, in which said means to apply a suction to said space comprises means to apply a vacuum to said space. 